Posterior intervertebral disc inserter and expansion techniques

ABSTRACT

Insertion and expansion devices for use in inserting motion discs, and associated methods of use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.12/055,779 filed Mar. 26, 2008, the disclosure of which is herebyincorporated by reference as if set forth in its entirety herein.

BACKGROUND OF THE INVENTION

The leading cause of lower back pain arises from rupture or degenerationof lumbar intervertebral discs. Pain in the lower extremities is causedby the compression of spinal nerve roots by a bulging disc, while lowerback pain is caused by collapse of the disc and by the adverse effectsof articulation weight through a damaged, unstable vertebral joint. Oneproposed method of managing these problems is to remove the problematicdisc and replace it with a prosthetic disc that allows for the naturalmotion between the adjacent vertebrae (“a motion disc”).

There are many types of motion disc inserters disclosed in the priorart. These devices generally hold the inferior and superior endplates ofthe motion disc for “line of site” insertion. Positive stops andmeasurement devices are also employed on these inserters to determinethe appropriate depth of implant placement.

PCT Published Patent Application WO 2006-058281 (“Glenn”) discloses aspinal implant to be inserted between two vertebra to support andstabilize adjacent vertebra and allow for physiological motion. Theinvention includes an implantable device to support the vertebrae, and aminimally invasive method for inserting and deploying the device withinthe intervertebral space.

SUMMARY OF THE INVENTION

The present invention relates to insertion and expansion devices for usein inserting intervertebral motion discs, and associated methods of use.They are grouped into two separate devices and techniques as follows:

In a first embodiment, the inserter has a longitudinal handle having adistal pair of holders for holding a proximal end of a pivoting motiondisc, wherein one of the holders is axially deployable within thehandle. The pair of holders secure the proximal legs of the implant forinsertion into the disc space. This assembly utilizes an implant firstmethodology, wherein this assembly is inserted into the disc space in anorientation wherein the implant is on the leading end of the assembly.Once the motion disc is placed into the disc space, a secondary deployerassociated with the handle is activated to axially move one of theholders, thereby moving one of the legs relative to the other leg andthereby changing the disc device footprint (e.g., pivoting one of thelegs). Several expansion mechanisms can be used to expand the legs ofthe implant.

The approach used in conjunction with this first embodiment may includeone or more annular locations. For example, in some embodiments, theapproach is ipsilateral. In some embodiments, the approach iscontralateral, or both. In some embodiments, the first embodiment of thepresent invention produces an X-shaped artificial intervertebral disc inits expanded condition. However, other expanded motion disc geometries,such as an H-shape artificial intervertebral disc in its expandedcondition, are also contemplated.

Therefore, in accordance with the present invention, there is provided amethod of inserting a curvilinear motion disc having a first and secondlegs connected by a pivot, each leg having an endportion, the methodcomprising the steps of:

-   -   a) providing the motion disc in a collapsed position,    -   b) providing a motion disc inserter comprising a handle having a        longitudinal axis and a first end having first holder and a        deployer, the deployer being axially moveable along the axis of        the handle,    -   c) attaching the first endportion of the motion disc to the        first holder,    -   d) contacting the second endportion of the motion disc to the        deployer,    -   e) arcuately inserting the motion disc into the disc space in        the collapsed condition, and    -   f) axially moving the deployer to move the second leg and to        expand the motion disc into an open condition.

Therefore, in accordance with the present invention, there is providedan assembly for inserting a curvilinear motion disc into a disc space,the assembly comprising:

-   -   a) a curvilinear motion disc having first and second pivoting        legs, each leg having an endportion, wherein the first and        second leg endportions are in a first collapsed position, and        wherein the first and second leg endportions are in a second        expanded position, and    -   b) an inserter comprising a handle having a longitudinal axis        and a first end having a first holder and a deployer, the        deployer being axially moveable along the axis of the rod,        wherein the first endportion of the motion disc is attached to        the first holder, and wherein the second endportion of the        motion disc is attached to the deployer.

In a second embodiment, the insertion instrument possesses an insertiontrack. The insertion track instrument is inserted into the disc space byitself and creates an annular shield for the motion disc implant(thereby protecting the disc). It also provides a guide or track for thesubsequently-placed motion disc implant insertion and placement tofollow during insertion. Lastly, the guide/track facilitates expansionof the motion disc footprint by holding the central axis pivot point.

-   -   Therefore, in accordance with the present invention, there is        provided a method of inserting a curvilinear motion disc having        first and second endportions, the method comprising the steps        of:    -   a) providing the motion disc in a collapsed position wherein the        first and second endportions are close together,    -   b) inserting into a disc space a distal portion of a motion disc        inserter comprising a tubular proximal portion and a curved        distal portion comprising upper and lower rails,    -   c) advancing the motion disc in the collapsed condition through        the motion disc inserter to insert the motion disc into the disc        space and rotate the motion disc, and    -   d) expanding the motion disc into an open condition in the disc        space.

The methods of the present invention differ from those of the prior artbecause the present methods employ non-linear insertion techniques withinstruments having deployment features that expand or change thefootprint of an artificial intervertebral disc implant.

Some embodiments of this invention differs from prior art because itemploys an expansion means to change location and footprint of theartificial disc, wherein the expansion means is independent of theinsertion method.

This invention differs from the prior art because it does not use screwattachment to couple the inserter to the implant.

DESCRIPTION OF THE FIGURES

FIG. 1 discloses inserting a first motion disc/inserter assembly intothe disc space, wherein the motion disc is in a collapsed condition.

FIG. 2 discloses advancing the motion disc of FIG. 1 further into thedisc space to rotate the motion disc.

FIG. 3 discloses the initial actuation of the deployer to expand themotion disc to a partially expanded condition.

FIG. 4 discloses the complete actuation of the deployer to expand themotion disc to a final expanded condition.

FIG. 5 discloses advancing a motion disc up a linear proximal portion ofa second motion inserter, wherein the motion disc is in a collapsedcondition.

FIG. 6 discloses further advancing the motion disc of FIG. 5 through acurved intermediate portion of the inserter to rotate the motion disc.

FIG. 7 discloses further advancing the motion disc of FIG. 6 through acurved distal portion of the inserter to insert the motion disc into thedisc space.

FIG. 8 discloses the final placement of the motion disc of the FIG. 7 inthe disc space.

FIG. 9 discloses advancing an H-type motion disc up a linear proximalportion of a second motion inserter, wherein the motion disc is in acollapsed condition.

FIG. 10 discloses further advancing the motion disc of FIG. 9 through acurved distal portion of the inserter to rotate the motion disc andinsert the motion disc into the disc space.

FIG. 11 discloses the initial actuation of the motion disc of FIG. 10 toexpand a first leg of the motion disc.

FIG. 12 discloses the final actuation of the motion disc of FIG. 11 toexpand a second leg of the motion disc.

DETAILED DESCRIPTION

Now referring to FIGS. 1-4, there is provided a method of inserting amotion disc having a first and second legs connected by a pivot, eachleg having an endportion, the method comprising the steps of:

-   -   a) providing the motion disc 1 in a collapsed position wherein        the first 3 and second 5 leg endportions are close together,    -   b) providing a motion disc inserter 7 comprising a handle having        a longitudinal axis and a first end 11 having first 13 and        second holders, the deployer being axially moveable along the        axis of the handle,    -   c) attaching the first endportion of the motion disc to the        first holder,    -   d) attaching the second endportion of the motion disc to the        deployer,    -   e) inserting the motion disc into the disc space in the        collapsed condition, and    -   f) axially moving the deployer to move the second leg and to        expand the motion disc into an open condition.

In particular, and now referring to FIG. 1, the motion disc insertersecures the proximal portion of the motion disc implant for insertioninto the disc space by grasping the top and bottom aspects of theproximal portion of the intradiscal device. Now referring to FIG. 2, theimplant is inserted into its desired location in the disc space.

Now referring to FIG. 3, with the implant in its desired location, thedeployment component of the inserter is activated to expand or adjustthe implant shape for improved vertebra body contact and balanced loadtransfer. In particular, the expansion component of the inserter isactivated to move the deployer axially and thereby pivot one of the legsof the implant shape. This produces expansion of the implant, improvedvertebra body contact and a more balanced load transfer. Means for theaxial movement of the deployer (and thereby the second leg) include: a)a rod that is slideably movable within a tube, b) a threaded rod that isthreadably movable within a threaded tube, and c) a notched rod that iscapable of ratcheted actuation.

FIG. 4 shows the motion disc in its expanded condition after it has beenexpanded by activation of the inserter.

The extent to which the deployer can be axially moved can be monitoredvia depth markings. In some embodiments, the depth markings are placedon the deployer. In some embodiments, the depth markings are placed onthe insertion handle.

Although the inserter/deployer is shown in FIGS. 1-4 as being utilizedin a posterior approach, it can be also used for other angles ofapproach, including lateral, anterior, and postero/lateral approaches.

The implant used in conjunction with the first embodiment can be ofvarying shape and configurations. Typically, it has at least onepivoting leg. In some embodiments, it has a pair of pivoting legs. An “Xshaped” implant is shown in FIGS. 1-4. The X-shape can have multiplelayers wherein inferior and superior layers are held or deployedindividually or simultaneously. Other disc implant geometries canutilizes the inserter holder/deployer of the first embodiment to insertan implant and change the footprint via disclosed the deployment means.An example of an alternate geometry is a “T”-, “Y”- or “H”-shapedimplant.

In some embodiments, the handle portion of the present inventioncomprises a tube within which the deployer is contained. In someembodiments, the first holder is fixedly attached to the distal endportion of the tube. In other embodiments, the handle portion of thepresent invention comprises a solid rod, and the holders are attached tothe outer surface of the rod.

The insertion track of the second embodiment of the present invention iscurvilinear and has a blade, semi-tubular or tubular construction,thereby allowing negotiation of bony or soft tissues without damagingthose tissues. This track provides a fixed route for insertion androtation of the motion disc. In some embodiments, it has a substantiallylinear proximal portion and a curved distal portion. In someembodiments, the linear proximal portion is tubular. In someembodiments, the curved distal portion can also be tubular. However, inother embodiments, the curved distal portion can comprise upper andlower rails that mate with the upper and lower aspects of the motiondisc. The insertion track also allows insertion of the motion disc via atrajectory more comparable to that of the inner wall of the annulusfibrosus, as compared to “line of site” linear insertion techniques.This compatible trajectory has the advantage of intruding upon less ofthe annulus fibrosus during device insertion. In use, the track isinserted into the disc space prior to insertion of the motion disc.Doing so creates an annular shield around the implant so that theimplant can be safely inserted into the disc space. The curved featureof the insertion track also creates a guide for turning the deviceduring device placement. It may also provide a method of changing thedevice footprint by virtue of a guiding pusher for expansion of shape.

Now referring to FIG. 5, there is provided an insertion track 21 of thepresent invention following its insertion into the disc space along theannular inner wall.

Now referring to FIG. 6, a motion disc implant 23 is shown advancingalong this insertion track to enter the disc space. Now referring toFIG. 7, the implant is advanced along the track until its final desiredcentral placement is obtained. The placement depth can be limited by apositive stop(s) along the insertion track (proximal tip stop (notshown). The depth to which the implant is inserted into the disc spacecan be monitored via depth markings provided on the track andreferencing off an adjacent vertebral body.

Several methods of advancing the device along the insertion track can becarried out in accordance with the present invention. These methodsinclude using a pusher instrument that holds and pushes the proximal endof the implant to advance it distally along the track. Another possiblemethod may use a puller comprising a cable wrapped around a pulleylocated at the distal tip of the track, wherein one free end of thecable is connected to the implant and the other free end extends out ofthe proximal tubular portion of the insertion track. In this case,providing a tensile or pull force on the cable moves the device distallyalong the track and into the disc space.

Various methods of deployment can be used to change the device footprintonce the motion disc is placed within the disc space. In one embodiment,the method includes temporarily attaching interconnecting features thatconnect the insertion track to the implant, and withdrawing theinsertion track from the disc space, thereby changing the footprint ofthe implant via the insertion track extraction forces. In a secondembodiment, and now referring to FIG. 8, the method includes placing onthe contra-lateral side of the disc space an instrument to create anadvancement stop. Instrument 31 has a puller mechanism, activating thepuller mechanism and pulling or pushing the motion disc into position Inalternate embodiments, the contralateral puller or pusher mechanism maybe actuated to change the footprint configuration of the motion disc.

In some embodiments, the insertion track can be directly connected tothe implant, which provides the advantage of controlled trajectory andfinal position. In other embodiments, the insertion track can beconnected to a holder/spacer that is attached to the implant and theinsertion track, which provides the advantage of determining the angleof approach and entry for the puller/pusher mechanism.

The implant used in conjunction with the second embodiment can be ofvarying shape and configurations. Typically, it has at least onepivoting leg. In some embodiments, it has a pair of pivoting legs. AnX-shaped implant is shown in FIGS. 5-8. The X-shape can have multiplelayers, wherein various inferior and superior layers are held and/ordeployed individually or simultaneously. Other disc implant geometriescan exploit the insertion track to insert an implant and change thefootprint via disclosed deployment means. In some embodiments, thealternate implant geometry comprises a “T”-, “Y”- or “H”-shaped implant.

FIGS. 9-12 disclose the insertion and actuation of an H-type motion discusing the insertion track inserter of the present invention. This motiondisc has a central body 51 having first 53 and second 55 endportions,wherein a first leg 57 is pivotally attached to the first endportion ata first pivot, and wherein a second leg 61 is pivotally attached to thesecond endportion at a second pivot. Upon expansion, each of the legs ofthis device pivots to an orientation perpendicular to the longitudinalaxis of the central body, and the device takes on an “H” shape.

Now referring to FIG. 9, an H-type motion disc in a collapsed conditionis advanced up a linear portion of the insertion track inserter. Nowreferring to FIG. 10, the H-type motion disc is further advanced througha curved portion of the insertion track inserter to rotate the motiondisc and insert the motion disc into the disc space. Now referring toFIG. 11, initial actuation of the motion disc causes the pivoting offirst leg of the motion disc and initial expansion of the motion disc.Now referring to FIG. 12, final actuation of the motion disc causespivoting of the second leg of the motion disc and complete expansion ofthe motion disc.

Irrespective of the embodiment selected, if desired, an optional guide101 (shown in FIG. 8) can be utilized during insertion and deployment toassist the surgeon in any one of disc space distraction, implantpositioning, implant expansion, and/or verifying implant placement. Thisguide is typically placed on a contralateral side of the disc space.When the guide is used as a distractor, it typically has a transversecross-section having a height and a width, wherein the width is greaterthan the height. The distractor is inserted into the disc spacecontralaterally so that its height dimension bears against theendplates. Prior to insertion of the motion disc, the distractor isrotated 90 degrees so that its width dimension now bears against theendplates, thereby increasing the height of the disc space.

Irrespective of the embodiment selected, in some embodiments, theinserter/deployer (as shown in FIGS. 1-4) or the insertion track (asshown in FIGS. 5-8) is used in a freehand manner. However, in otherembodiments, the inserter/insertion track further comprises a dockingmeans to dock onto or reference off nearby stable landmarks such as avertebral body edge or a pedicle screw. Docking off of these locationsprovides for enhanced surgical stability and control.

Irrespective of the embodiment selected, intraoperative imagingtechniques (including fluoroscopy) can be used to assist in or verifyplacement and deployment of the inserter and/or motion disc. Althoughthe primary surgical approach shown is posterior or posterior/lateral,other approaches can be utilized.

Although the inserter/deployer and insertion track inserters are shownas being utilized posteriorly, they can be also used for other angles ofapproach including lateral, anterior, and posterior/lateral approaches.

1. (canceled)
 2. An intervertebral implant, comprising: a) a centralbody having a longitudinal axis, a proximal endportion and a distalendportion, b) a first leg pivotally attached to the proximalendportion, wherein the first leg has a first orientation substantiallyin-line with the longitudinal axis of the central body to provide afootprint, wherein the first leg pivots to produce a second orientationsubstantially perpendicular to the longitudinal axis of the centralbody, and wherein the second orientation changes the footprint of theimplant.
 3. The implant of claim 2, wherein the longitudinal axis of thecentral body is a curvilinear longitudinal axis.
 4. The implant of claim2, wherein the leg contacts an adjacent vertebral body.
 5. The implantof claim 2, wherein the central body has an intermediate portioncomprising a convex sidewall and a concave sidewall, wherein the convexsidewall is substantially parallel to the concave sidewall.
 6. Theimplant of claim 2, wherein the first leg constitutes an upper surfaceof the implant.
 7. An intervertebral implant, comprising: a) a centralbody having a longitudinal axis, a proximal endportion and a distalendportion, b) a first leg pivotally attached to the proximalendportion, wherein the first leg has a proximal face substantiallyperpendicular to the longitudinal axis of the central body, and whereinthe first leg is pivotable so that the proximal face can becomesubstantially parallel to the longitudinal axis of the central body. 8.The implant of claim 7, wherein the longitudinal axis of the centralbody is a curvilinear longitudinal axis.
 9. The implant of claim 7,wherein the leg contacts an adjacent vertebral body.
 10. The implant ofclaim 7, wherein the central body has an intermediate portion comprisinga convex sidewall and a concave sidewall, wherein the convex sidewall issubstantially parallel to the concave sidewall.
 11. The implant of claim7, wherein the first leg constitutes an upper surface of the implant.12. An assembly comprising: i) an intervertebral implant, comprising: a)a central body having a longitudinal axis and proximal and distalendportions, and b) a first leg pivotally attached to the proximalendportion, wherein the first leg has a first orientation substantiallyin-line with the longitudinal axis of the central body to provide afootprint, wherein the first leg pivots to produce a second orientationsubstantially perpendicular to the longitudinal axis of the centralbody, and wherein the second orientation changes the footprint of theimplant ,and ii) an inserter attached to the first leg of theintervertebral implant.
 13. The implant of claim 12, wherein thelongitudinal axis of the central body is a curvilinear longitudinalaxis.
 14. The implant of claim 12, wherein the leg contacts an adjacentvertebral body.
 15. A method of inserting the intervertebral implant ofclaim 2 into a disc space, comprising the steps of: a) attaching aninserter to the first leg of the intervertebral implant, b) insertingthe intervertebral implant into the disc space using the inserter, c)pivoting the first leg of the inserted implant.
 16. The method of claim15, wherein the inserting step includes initially inserting the implantso that the longitudinal axis of the central body has a substantiallyanterior-posterior orientation in the disc space.
 17. The method ofclaim 16, wherein the inserting step include rotating the implant sothat the longitudinal axis of the central body has a substantiallylateral orientation in the disc space.
 18. The method of claim 17,wherein the first leg pivots to an orientation substantiallyperpendicular to the longitudinal axis of the central body.
 19. Themethod of claim 18, wherein the first leg pivots while the central bodyrotates.
 20. The method of claim 19, wherein the first leg residessubstantially anterior to the rotated, inserted central body after stepc).
 21. The method of claim 20, wherein the leg contacts a vertebralbody adjacent the disc space.
 22. The method of claim 20, wherein thecentral body has an intermediate portion comprising a convex sidewalland a concave sidewall, wherein the convex sidewall is substantiallyparallel to and anterior to the concave sidewall.
 23. An intervertebralimplant for insertion between upper and lower vertebral endplates,comprising: a) a central body having a longitudinal axis, a proximalendportion, a distal endportion, and b) a first leg pivotally attachedto the proximal endportion, wherein the first leg has a firstorientation substantially in-line with the longitudinal axis of thecentral body to provide a first cross-sectional perimeter, wherein thefirst cross-sectional shape is defined in a plane parallel to anendplate, and wherein the first leg pivots to produce a secondorientation substantially perpendicular to the longitudinal axis of thecentral body to provide a second cross-sectional perimeter defined inthe plane parallel to an endplate, and wherein the first cross-sectionalperimeter is different than the second cross-sectional perimeter.